Quad damage

From DoomWiki.org

Quad damage as seen in the game

The quad damage power-up temporarily multiplies the Doom Slayer's attack damage by four, allowing elimination of enemies much easier and with less use of ammunition. The power-up itself comes in the form of a purple fireball suspended in the air, with an animation of a moving skull overlaying it visible when examined closely. While active, a purple aura will be seen around the edges of the screen, as well as around the view model of the player's arms and weapons. Firing weapons while quad damage is active will cause a sound effect derived from the one used for the same power-up in the Quake series of games.